1. Field of the Invention
The present invention relates to the field of audio signal processing systems. More particularly, the present invention relates to the field of automatic gain controllers.
2. Description of the Prior Art
In broadcasting and recording it is often desirable to use a device which can function as an automatic level controller. The function of such a device is to maintain the outgoing signal reasonably close to the reference level even though the incoming signal may vary over a wide range of levels. The advantages of using such a device depend on the type of application, but generally the advantages are improved listenability of a string of programming elements such as music selections, announcements, and commercials. Also, in recording, vocal tracks and submixes can sometimes be better mixed into the final cut if automatic level control is used for the separate tracks.
Automatic level controllers (hereafter referred to as "the leveler") are usually referred to as "AGC" which represents automatic gain controllers. An ideal leveler would take a wide range of input audio levels and produce at the output a well regulated level which remains, on the long term average (i.e. based on a 10 second or longer average), near the specified reference level. An ideal leveler would also allow the shorter term dynamics of the sound to remain natural without compression or limiting effects due to the leveling action. An ideal leveler would further perform its function without being obvious to a listener. In other words, a leveler should keep the sound very natural, but at a consistent audio level. It is not necessarily obvious or simple to accomplish the above objectives, since the ear is usually very sensitive to the effects of dynamic range compression.
There are a number of products on the market called levelers which have a selectable function called leveling. Typically, these levelers do not closely meet all of the above described ideal levelers. Therefore, it would be desirable to create a new leveler which would more closely resemble the above described ideal levelers and which is both easy to use and low in cost.